A version of this article was originally published in the December 2015 issue of Clarion, the newspaper of the Professional Staff Congress-CUNY.

On Monday, the Supreme Court will take up Friedrichs v. California Teachers Association, a case with profound implications for the future of public-sector labor unions, and the labor movement as a whole. At issue is the underpinning of public-sector unionism—that public employees who opt out of union membership can still be obligated to pay for their individual share of the services and collective bargaining they receive from the union. The Court could even decide to make union membership an opt-in rather than an opt-out proposition, allowing the public employees unions are required to represent to glean the benefits of representation without paying dues.

While the plaintiffs in Friedrichs base their claims on a free speech argument that many find dubious, tucked away in the case lies another, real First Amendment concern: the separation of church and state. The lead plaintiff in the challenge before the High Court is Rebecca Friedrichs, a teacher in California’s Savanna School District; she is joined in the suit by nine additional individuals, and one organization: the Christian Educators Association International (CEAI), which bills itself as an alternative to the “secular” teachers’ unions, and argues openly that the Constitution does not bar teachers from imparting their Christian faith in their classrooms.

Should those unions find themselves on the losing side of the Friedrichs case, an important bulwark against the incursion of religion in public schools will be undermined.

“Many public-school educators believe that they must make their schools God-less under the banner of ‘separation of church and state,’” CEAI’s executive director, Finn Laursen, has written, “to the extent that an environment is created that is hostile to religion.”

The teachers’ unions, Laursen maintains, “have such control that student needs become secondary” to those of the union. In that “hostile” public-school environment, according to Laursen, “the sin nature [sic] of mankind is accepted and even promoted.” There are “forces are at work,” he writes, that aim to “control the minds of our children by systematically promoting such things as sexual orientation being genetically driven and same sex marriage being acceptable under the banner of tolerance.”

Representing CEAI and the other plaintiffs is the Center for Individual Rights, a pro-bono law firm whose donors are linked to the Koch brothers, the billionaires known for their opposition to labor unions.

The CEAI casts public schools as settings ripe for proselytizing, and its members as the foot soldiers in a battle for the students’ minds—and souls. “There are over 50 million students in our public schools, 70 million parents, three and a half million teachers,” Laursen said in a 2007 video titled “Christian Teacher Core Values.” That represents nearly 124 million people, he added, “many of them spiritually and morally bankrupt. We know the truth, and we need to send our missionaries into that area.”

In its brief asking the Supreme Court to take up the Friedrichs case, a petition the Court granted in June, CEAI makes no mention of its positions on church-state separation, secularism, or its conservative Christian beliefs. But in materials disseminated through its website, in media interviews, and at its events, CEAI makes clear that it aims to help teachers skirt the Constitution by claiming that their right to free religious expression is thwarted by the separation of church and state.

This strikes directly at the First Amendment’s Establishment Clause, which states that the government, including public schools, may not endorse or appear to endorse a particular religion. CEAI officials have claimed that this principle is not in the Constitution; in fact, one has called the assertion of constitutional church-state separation “a lie.”

Laursen declined to be interviewed for this article.

Founded in 1953 in California as the Fellowship of Christian Educators, CEAI now presents itself as an alternative to the National Education Association (NEA), which it claims promotes secular, liberal political positions that conflict with Christian values. The association currently has chapters in 20 states; its website says its mission is “to encourage, equip, and empower educators according to biblical principles.”

The history of evangelical involvement in anti-union activity dates back at least to the 1930s, according to Baruch College history professor Clarence Taylor. At the time, many conservative evangelicals viewed unions as part of a supposed communist threat, and business-allied leaders, such as James Fifield and Abraham Vereide, organized events to evangelize against the New Deal. (Vereide convened prayer breakfasts for business elites and Fifield founded the Spiritual Mobilization movement.) The fear of unions intensified in evangelical circles during the Cold War and amid the backlash against movements for racial equality and women’s rights. In 1979, the newly founded Moral Majority played a significant role in electing Ronald Reagan to the presidency.

“When looking at that long history, clearly by the 1970s, the Christian right decided to get involved in politics,” Taylor said in a telephone interview. “They particularly targeted unions because they saw them as strong opposition to their agenda,” including officially sanctioned prayer in public schools.

Not that all evangelicals hew to an anti-union line. Many evangelicals not only support but belong to labor unions, said Ken Estey, an associate professor of political science at Brooklyn College. A monolithic view of their position on unions, said Estey, “doesn’t capture the complexity in American evangelicalism, especially on the social justice side.”

The legal claims in Friedrichs rest on the assertion that paying agency fees (also described by unions as “fair share” fees) to the California Teachers Association violates the plaintiffs’ free speech rights because of their disagreements with CTA’s political positions. But agency-fee payers—teachers who have opted out of union membership, and are consequently mandated only to pay for their share of services the union provides on their behalf, such as collective bargaining—are not required to pay for the union’s political activities.

But in Friedrichs, CEAI argues that the Christian group and its 600 California members—including six of the individual plaintiffs in Friedrichs—are “fundamentally opposed to many of the positions taken by teachers’ unions, both within the collective bargaining process and outside of that process.” The group’s argument frames the collective-bargaining process as an expression of politics in and of itself, and therefore a violation of the freedom of association guaranteed under the First Amendment.

In a section of its website devoted to warning prospective members of the National Education Association’s “liberal political stance,” CEAI notes, “You may also be surprised at what you find as you compare your Christian beliefs with the agendas of the NEA and realize your membership dollars makes [sic] the NEA’s agenda possible.”

Furthermore, CEAI maintains, California’s agency shop laws have the “effect of creating a drain on CEAI’s resources.” According to Laursen’s affidavit filed in the case, the “scheme operated by” the teachers’ union causes CEAI to spend money counseling its members on how they can opt out of union fees based on religious objections, rather than spending money on other services for its members.

Those services include providing backing to CEAI’s member teachers when their school districts censure them for crossing that church-state separation line.

The CEAI, Laursen has said, is “here to encourage, equip, and empower Christian educators in our public schools … to become transformational agents.” The organization will, according to its website, offer members “prayer support,” “guidance on establishing prayer groups in your building,” and connections with “ministries that equip you to be an effective witness for Jesus our Lord in your school or district.”

CEAI often takes positions that are in conflict with prevailing law on the major church-state separation issues in the public schools. In 2006, after a federal judge in Pennsylvania ruled in Kitzmiller v. Dover Area School District against teaching “intelligent design”—a theory that life and the universe were created by an intelligent entity—in public schools as a violation of the Constitution, Laursen insisted that teachers be permitted to teach “the controversy,” terminology creationists use to portray the teaching of creationism as simply another viewpoint. (One of the benefits of CEAI membership is discounted tickets to the Creation Museum in Petersburg, Kentucky.)

But CEAI’s educational agenda, however popular with its members, has consistently been rejected in the courts. With the exception of its anti-union claims in the Friedrichs case, CEAI’s forays into the legal system have involved what it has framed as the defense of teachers expressing their faith in the classroom. These assertions have been routinely rejected by the courts as violating the First Amendment’s Establishment Clause.

In 2010, Laursen served as an expert witness in hearings reviewing the termination of John Freshwater, a middle school science teacher in Mount Vernon, Ohio, who was fired in 2008 for refusing to follow school district directives to remove displays of religious texts and the Ten Commandments from his classroom. Freshwater’s troubles began in 2007 when a student sued the school district, alleging that the veteran teacher had burned a cross into the student’s arm with a Tesla coil. The school district settled the case with the student out of court.

In CEAI’s Teachers of Vision Magazine, Laursen recounted his testimony at Freshwater’s administrative proceedings challenging the teacher’s dismissal. “I invested over two hours clarifying the religious freedoms teachers have in our public schools that were relevant in Mr. Freshwater’s case,” Laursen wrote. “All the pieces of the testimony lined up with the key issues of the case and the peace of the Lord could be felt during the process.”

When Freshwater filed a separate federal case against the school district, claiming that its actions violated his First Amendment right to his free exercise of religion, Laursen said in a statement that he was “happy to serve someone of such high moral character as John Freshwater as a member of CEAI. John is proving to be a hero of the faith.”

Although Freshwater ended up dropping his First Amendment case against the district, his appeal of his termination went all the way to the Ohio Supreme Court, which ruled in his employer’s favor in 2013. Chief Justice Maureen O’Connor wrote in the majority opinion that Freshwater “not only ignored the school district’s directive, he defied it.” He did not have a “Free Exercise” right to display those items in his classroom, she added, “because they were not a part of his exercise of his religion. Freshwater’s willful disobedience of these direct orders demonstrates blatant insubordination.” The U.S. Supreme Court denied review of the case in 2014.

CEAI also sought to intervene in a case in the Santa Rosa School District in Florida, where, in 2009, the school district had settled a lawsuit brought by the American Civil Liberties Union, that had charged numerous Establishment Clause violations. The school district’s conduct was “over the top,” said Daniel Mach, director of the ACLU Program on Freedom of Religion and Belief, who cited a high school teacher handbook that required school personnel to “embrace every opportunity to inculcate, by precept and example, the practice of every Christian virtue.” Mach said that teachers and coaches regularly led students in prayer, and some teachers “were effectively teaching Sunday school lessons in public school classes” and “proselytizing students, sometimes with a bullhorn.”

The school district admitted liability and agreed to a comprehensive settlement. But CEAI, represented by a religious-right law firm known as Liberty Counsel—the same outfit that represented the Kentucky clerk Kim Davis in her quest to deny marriage licenses to same-sex couples last year—intervened in a bid to vacate the consent decree. “They invented these fanciful readings of the consent decree,” said Mach. These included concerns that teachers would be barred from saying, “God bless you” if someone sneezed, or—in the case of one CEAI member—from praying quietly in the stands if her grandson, who attended school in the district, was injured in a wrestling match.

The court ruled their fears “objectively unreasonable,” a “strained interpretation of the decree,” and denied CEAI’s motion to intervene. The CEAI later brought its own lawsuit, which resulted, in 2011, in only minor clarifications of the consent decree, such as spelling out that saying “God bless you” does not violate the Establishment Clause.

Although it is not apparent from reading CEAI’s Supreme Court brief, if the Friedrichs plaintiffs are successful, the ripple effect of their efforts could do more than undermine unions: It could open another chapter in the war over religion in public schools, emboldening groups such as CEAI to intensify efforts to allow public school teachers to endorse and promote religion with their students once their best-organized opponents—the teachers’ unions—are weakened.